The effects group contain the weird kids (local contrast, sharpness, high/low-freq, retouch, liquify, etc.)
| The watermark module provides a way to render a vector-based overlay onto your image. Watermarks are standard SVG documents and can be designed using Inkscape. |
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The SVG processor of darktable also substitutes strings within the SVG document, which gives the opportunity to include image dependent information in the watermark such as aperture, exposure time and other metadata.
User-designed watermarks are placed into the directory $HOME/.config/darktable/watermarks. Once in place, use the reload button at the right of the watermark file name to update the list of available watermarks to use.
Here follows a list of available variable strings that is supported for substitution within the svg document. Beside this list you can also use the variable strings defined in export selected module.
| $(DARKTABLE.NAME) | The application name |
| $(DARKTABLE.VERSION) | The version of darktable |
| $(WATERMARK_TEXT) | A short free text (max. 63 characters) |
| $(WATERMARK_COLOR) | The color to use for $WATERMARK_TEXT |
| $(WATERMARK_FONT_FAMILY) | The font family to use for $WATERMARK_TEXT |
| $(WATERMARK_FONT_STYLE) | The font style (normal, oblique, italic) |
| $(WATERMARK_FONT_WEIGHT) | The font weight (boldness) |
| $(IMAGE.ID) | The unique image id within current library |
| $(IMAGE.FILENAME) | The image filename |
| $(IMAGE.BASENAME) | The image file basename |
| $(IMAGE.EXIF) | The image Exif string |
| $(EXIF.DATE) | The image date |
| $(EXIF.DATE.SECOND) | Seconds from the image Exif data |
| $(EXIF.DATE.MINUTE) | Minutes from the image Exif data |
| $(EXIF.DATE.HOUR) | Hours from the image Exif data (24h) |
| $(EXIF.DATE.HOUR_AMPM) | Hours from the image Exif data (12h, AM/PM) |
| $(EXIF.DATE.DAY) | Day of month from the image Exif data (01 .. 31) |
| $(EXIF.DATE.MONTH) | Month from the image Exif data (01 .. 12) |
| $(EXIF.DATE.SHORT_MONTH) | Month from the image Exif data localized (Jan, Feb, .. Dec) |
| $(EXIF.DATE.LONG_MONTH) | Month from the image Exif data localized (January, February, .. December) |
| $(EXIF.DATE.SHORT_YEAR) | Abbreviated year from the image Exif data (2013 is "13") |
| $(EXIF.DATE.LONG_YEAR) | Full year from the image Exif data |
| $(DATE) | Current system date |
| $(DATE.SECOND) | Current system time seconds |
| $(DATE.MINUTE) | Current system time minutes |
| $(DATE.HOUR) | Current system time hours (24h) |
| $(DATE.HOUR_AMPM) | Current system time hours (12, AP/PM) |
| $(DATE.DAY) | Current system time day of month (01 .. 31) |
| $(DATE.MONTH) | Current system time month (01 .. 12) |
| $(DATE.SHORT_MONTH) | Current system time month localized (Jan, Feb, .. Dec) |
| $(DATE.LONG_MONTH) | Current system time month localized (January, February, .. December) |
| $(DATE.SHORT_YEAR) | Current system time year (abbreviated) |
| $(DATE.LONG_YEAR) | Current system time year |
| $(EXIF.MAKER) | The maker of camera model |
| $(EXIF.MODEL) | The camera model |
| $(EXIF.LENS) | The specific lens used |
| $(Xmp.dc.creator) | The creator string |
| $(Xmp.dc.publisher) | The publisher string |
| $(Xmp.dc.title) | The title of the image |
| $(Xmp.dc.description) | The description of the image. This is the field to use when you're looking for the user-specified text that some cameras add at shoot time to exif field “User Comment” (also called “Exif.Photo.UserComment”). |
| $(Xmp.dc.rights) | The rights assigned to the image |
| $(GPS.LATITUDE) | The image latitude coordinate (N/S 0 .. 90) |
| $(GPS.LONGITUDE) | The image longitude coordinate (E/W 0 .. 180) |
| $(GPS.ELEVATION) | The image elevation level (meters) |
| $(GPS.LOCATION) | All three coordinates (latitude, longitude, elevation) |
Choose the watermark of interest. You can use the reload button next to the combobox to update the list with all newly added watermarks.
A free text field with up to 63 characters which gets printed if the corresponding
watermark references it. An example is supplied as simple-text.svg.
This field shows the text color. Clicking on the colored field will open a color selector dialog which offers you a choice of commonly used colors, or allows to define a color in RGB color space.
This field lets you select the text font. Clicking on the field opens a dialog box which shows the fonts available to your system. Fonts can be searched by name and a preview of each available font is shown next to the font name; you may specify your own sample text. The font defaults to “DejaVu Sans Book”.
Defines the reference for the scale parameter. The default setting “image” scales the watermark relative to the horizontal image size. Alternatively you can scale the watermark relative to the “larger border” and “smaller border”, respectively.
| This module is an artistic feature to generate a frame around your image. The frame consists of a border with a user defined color and a frame line inside that border, which has another user defined color. There are various options for you to control the geometry of your frame. |
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With this combobox you can choose between different aspect ratios for the final output of this module, i.e. underlying image plus frame.
If you select a non-square aspect ratio this combobox defines the orientation – portrait or landscape. Set to “auto” if you want darktable to select the most reasonable orientation based on the underlying image.
Select from a set of pre-defined ratios where you want your underlying image be positioned on the horizontal axis. You can also right click and enter your own ratio as “x/y”.
Select from a set of pre-defined ratios where you want your underlying image be positioned on the vertical axis. You can also right click and enter your own ratio as “x/y”.
The percentage of the frame line size relative to the border size at its smallest part.
Where the frame line is positioned relative to the underlying image. Select a value of 0 for a frame line touching the image, 100% for a frame line touching the outer border limits.
A color selector which allows to define a color for the border. Clicking on the colored field will open a color selector dialog which offers you a choice of commonly used colors, or allows to define a color in RGB color space.
You can also activate a color picker by pressing
and take a color probe from your image. You can switch between point and area sampling
mode from within the global color picker panel (see
Section 3.3.6, “Global color picker”).
A color selector which allows to define a color for the frame. Clicking on the colored field will open a color selector dialog which offers you a choice of commonly used colors, or allows to define a color in RGB color space.
You can also activate a color picker by pressing
and take a color probe from your image. You can switch between point and area sampling
mode from within the global color picker panel (see
Section 3.3.6, “Global color picker”).
| This module is an artistic feature which creates vignetting (modification of the brightness/saturation at the borders). |
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The vignetting module has an extensive set of parameters to precisely tune its effect. It also will display graphical controls within the image if the module is in focus. Give it a try to get a feeling of how it works. On-screen controls and parameter sliders will stay in sync.
This module is known to provoke banding artifacts under certain conditions; you should consider to activate the dithering module (see Section 3.4.1.1, “Dithering”).
Sets the progressiveness of the fall-off. Higher values will cause a steeper transition.
Controls how strong colors become when desaturated or saturated in the darkened or brightened vignetting area.
Influences the shape of the vignetting area. The default value of 1 causes a circular or elliptical area. Smaller values will shift the shape into a more square one; higher values turn it into a cross-like shape.
Click this button to automatically adjust the width/height ratio of the vignetting area to the aspect ratio of the underlying image. The vignetting area will typically become elliptical.
With this combobox you can activate random noise dithering to overcome banding artifacts caused by vignette gradients. Select “8-bit output” to prevent banding on monitor display and for JPEGs. When set to “16-bit output”, only a little dithering will be applied, just strong enough to compensate for banding on the fine grained 16-bit level. This feature is mostly obsoleted by our new module dithering (see Section 3.4.1.1, “Dithering”).
| This module is an artistic feature that creates a softened image, commonly known as the Orton effect. |
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Michael Orton achieved his results on slide film by using two exposures of the same scene: one well exposed and one overexposed; he then used a darkroom technique to blend those into a final image where the overexposed image was blurred.
This module is almost a copy of Orton's analogue process into the digital domain. You can control brightness and blur with the provided parameters; we also add a control for saturation of the overexposured image for more play.
| This module is a quick way to convert an image into black and white and provides a variable color filter for that conversion. |
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A color picker is activated by pressing
and will automatically set the position and size of the filter. You can switch between
point and area sampling mode from within the global color picker panel (see
Section 3.3.6, “Global color picker”).
The default central location of the filter has a neutral effect but dragging it to an alternate position applies a filter analogously to taking a b&w photograph through a conventional color filter.
As well as position you can change the filter size by scrolling with your mouse wheel. This makes the filter's range of hues more or less selective.
Tip: First reduce the filter size to concentrate its effect and move it across the hue pallet to find the best filter value for your desired image rendition. Then expand the filter to include more hues and thus more natural tonality.
Under certain conditions, especially highly saturated blue light sources in the frame, this module may produce black pixel artifacts. See the gamut clipping option (Section 3.4.1.11, “Input color profile”) on how to mitigate this issue.
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The low light module allows one to simulate human lowlight vision, thus providing ability to make lowlight pictures look closer to reality. It can also be used to perform a day to night conversion. The idea is to calculate a scotopic vision image which is perceived by rods rather than than cones in the eye under low light. Scotopic lightness then is mixed with photopic value (regular color image pixel) using some blending function. Also this module is able to simulate the Purkinje effect by adding some blueness to the dark parts of the image. |
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This module comes with several presets. Give them a try to get a better feeling how it works.
The horizontal axis is about pixel lightness from dark (left) to bright (right). The vertical axis represents the kind of vision from night vision (bottom) to day vision (top)
| This module takes highlights, blurs them and then blends (screen blend lightness) with the original to create a soft blooms over the image, hence the name of the effect. There are numerous ways to use this module depending on the image's actual scenery lighting. |
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Starting from the default settings change the strength value for a pleasant look, then change the size to control the spread of light.
| This module allows enhancing local contrast. It supports two modes of operation: the default one uses a local laplacian filter, the other one uses the unnormalized bilateral filter. Both work exclusively on the L channel from Lab. |
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Local contrast boosts details of your image, much like the equalizer does (see Section 3.4.3.14, “Equalizer”). However, it is easier to use as it does not require you to work on different frequency bands. The local laplacian filter has been designed to be very robust against unwanted halo effects and gradient reversals along edges.
Choice of "local laplacian filter" or "unnormalised bilateral grid". The options for the bilateral grid are: coarseness, contrast, and detail. The local laplacian filter supports: detail, highlights, shadows, and midtone range. The local laplacian mode supports shadow lifting and highlight compression, similar to the shadows and highlights module.
How strongly the algorithm distinguishes between brightness levels. Increasing the value results in a more contrasty look.
To understand the parameters of the local laplacian filter, you can think of it as applying a curve to the image, similar to this picture:
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It will then be applied to the image in a way that works locally and avoids halo artifacts.
Add or remove detail. Higher values will increase local contrast. This will insert an S shaped element in the center of the curve, to increase or decrease local contrast. For monochrome images it is often possible to push this parameter to extreme settings without ridiculous results or artifacts.
This affects one end of the curve, effectively increasing or compressing contrast in the highlights. A low value will pull the highlights down.
Similar to the highlights parameter, this affects the other far end of the curve, and will increase or decrease contrast in the shadows. A higher value gives more contrast in the shadows. A lower value will lift the shadows and can effectively simulate a fill light. Note that this is done via local manipulation of the image, however: this means that a completely dark image cannot be brightened this way, only dark things in front of bright things will be affected.
This controls the extent of the S shaped part of the contrast curve. A larger value will make the S wider, and thus classify more values to be midtone range and fewer values to belong to the highlights and shadows part. In more high dynamic range settings it can be useful to reduce this value to achieve stronger range compression by lowering the contrast in the highlights and the shadows. Note however that for really strong HDR scenarios this may work best in combination with a base curve which pre-compresses the range, maybe with an approximately logarithmic base curve. Also the exposure fusion feature in the base curve module may lead to more pleasing results at times, but is more prone to producing halo effects.
This setting can cause banding artifacts in the image if pushed to extreme values. This is due to the way darktable computes the fast approximation of the local laplacian filter.
| This module transfers the look and feel from one image onto another. It statistically analyses the color characteristics of a source image and a target image. The colors of the source image are then mapped to corresponding colors of the target image. |
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To use this module two steps are required.
First you open the source image in darkroom mode and acquire its color characteristics by pressing the “acquire as source” button. A set of color clusters is generated and displayed in the “source clusters” area. Each cluster is represented by a set of color swatches with the mean value in the center surrounded by swatches indicating the color variance within that cluster. The clusters are sorted in ascending order by their weight, i.e. the number of pixels that contribute to the clusters.
Next you open your target image in darkroom mode. darktable has remembered the previously
collected source clusters; if they are not yet displayed, press the
button. You now press the “acquire as target” button to generate a
corresponding set of color clusters for your target image, which gets displayed in the
“target clusters” area.
When both source and target clusters are collected an automatic color mapping is applied to the target image. In its default settings the overall effect is quite exaggerated. A set of sliders gives you control of the effect's strength. You can also use blending operator “normal” to tame the effect (see Section 3.2.5.4, “Blending operators”). As the color mapping module comes early in the pixelpipe, you can finetune the colors with modules like tone curve (see Section 3.4.2.13, “Tone curve”) or color correction (see Section 3.4.2.7, “Color correction”).
Press these buttons to generate color clusters for the source and target image, respectively. The processing takes a few seconds during which the GUI remains unresponsive.
Sets the number of color clusters to use. If you change this parameter all collected color clusters are reset and need to be acquired anew.
This parameter controls the mapping between source and target clusters. At the lowest value mapping is based on color proximity. This typically leads to very subtle effects on the target image. At the maximum value mapping is based on the relative weight of the color clusters – dominant colors of the source image are mapped to dominant colors of the target image. This typically leads to a very bold effect. In-between values incrementally shift between the extremes.
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The source image taken shortly after sunset under front lighting conditions. | |
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The target image taken in the afternoon with a partly clouded sky. Our goal is to transfer the evening atmosphere of the source image. | |
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The target image with color mapping applied. A number of 2 clusters was used. “color dominance” is set to 100% for a bold but still credible effect. “histogram equalization” is set to 80%. |
This module works by enhancing the contrast around edges and thereby enhances the impression of sharpness of an image. In darktable this module is only applied to the L-channel in Lab color space.
USM applies a gaussian blur to your image as part of its algorithm. This controls the blur radius which in turn defines the spatial extent of edge enhancement. Too high values will lead to ugly over-sharpening.
| Highpass acts as a high pass filter. The primary usage for this filter is in combination with a blending operator. Try out blend mode “soft light” to get highpass sharpening. Use the opacity slider to adjust the strength of the effect or use a drawn mask (see Section 3.2.5.5, “Drawn mask”) or parametric mask (see Section 3.2.5.6, “Parametric mask”) to limit the effect to only parts of your image. |
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| A lowpass filter (eg. gaussian blur) with additional control of the outcome both of contrast and saturation. The primary usage for lowpass filter is in combination with a blending operator (see Section 3.2.5.4, “Blending operators”). Try out the preset named “local contrast mask” with an “overlay” blending operation. |
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This module offers enormous artistic potential, albeit, with results that are sometimes difficult to predict.
This combobox defines the blur algorithm; you can choose between “gaussian” blur (default) and “bilateral” filter. The latter leads to an edge preserving blur. “gaussian” will blur all image channels: L, a and b. “bilateral” will only blur L channel.
Changes the contrast. Negative values result in an inverted negative image. Higher absolute values increase contrast; lower absolute values reduce contrast. A value of zero leads to a neutral plane.
Changes the brightness. Negative values result in a darker image. Positive values increase the image's brightness.
| This versatile module can be used to achieve a variety of effects, such as: bloom, denoising, clarity, and local contrast enhancement. It works in the wavelet domain and parameters can be tuned for each frequency band separately. |
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Each frequency band can be tweaked independently. In particular, you can adjust contrast boost and denoise threshold splines for both lightness and chromaticity (“luma” and “chroma”), as well as the acuteness (“edges”) of the wavelet basis on each frequency scale.
| Each spline can be dragged with a proportional edit approach; use the mouse wheel to adjust the radius in which your changes will have an effect. The transparent area indicates where you would drag the spline with the current mouse position and radius. The small little triangles on the x-axis can be moved to alter the x-position of the spline nodes. |
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| Drag the upper line (bright circles, here for the lightness channel) to affect local contrast. Pulling it up, as shown here, will result in a contrast boost for that frequency band. Higher frequencies, i.e. smaller details, are to the right of the grid. Pulling it down works, too. |
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| The bottom spline (black circles) is used to perform denoising. It adjusts the wavelet shrinkage threshold for each frequency band. Pull it up to see the effect. In this example, the noise which has been amplified by local contrast enhancement is removed. |
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| This screen shows the effect of the edge parameter. It is here pulled down to zero for all bands. This is effectively a regular à trous wavelet, without edge detection, and results in the characteristic halos around sharp edges in the image. |
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Note that the edge parameter only affects the wavelet basis, not the image directly. You will have to change some denoise/contrast boost parameters to see an effect following adjustments to the edge parameter.
This module additionally has a “mix” slider below the spline GUI. Adjusting the slider will upscale or downscale the splines on the y-axis. The slider was added as a convenience tool to help you modify the strength of the effect. It is not a module parameter in itself; when you leave darkroom mode all changes will be consolidated into the spline curves.
Have a look at the presets where there are a broad variety of examples that will provide a good starting point to gain an intuitive understanding of the controls. Among others there is preset to enhance an image's “clarity”.
| Retouch allows to heal, clone, fill and blur certain areas of the image. It can perform a wavelet decomposition which separates the image into different frequency scales, from fine to coarse, and apply retouch operations to each wavelet scale individually. |
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For a basic use, with default parameters, add the shapes to the image like with the spot removal module (see Section 3.4.3.16, “Spot removal”). To use the wavelet decompose first select one of the scales as the current scale (see below) and then add the shapes.
The GUI is divided in three main sections: wavelet decompose, retouch tools and shapes.
The wavelet decompose toolbar controls the wavelet decompose algorithm. It has a central area divided in boxes and two sliders. The first box, scale zero, represents the original image, the second is the wavelet scale 1, and so on.
The bottom slider adjusts the number of scales, zero means no wavelet decompose is done. The maximum number of scales depends on the image size, but any number can be selected. If the image is not big enough for the selected number of scales the maximum number of scales for this image size is used and the rest of the scales are ignored.
The image is decomposed to the selected number of scales plus the residual image, so if 5 is selected as the number of scales, scale zero is the original image, scales 1 to 5 are the detail scales, and scale 6 is the residual image. As a visual aid, the original image is always represented by a black box, detail scales are light gray, residual image white and inactive scales dark gray.
The central area allows to select the current scale on which the user can then apply retouch tools by left clicking any of the boxes. The selected scale is marked by a red frame. Any scale can be selected as the current scale, even if it is greater than the number of scales. If a shape is added to a scale greater than the residual image it will be ignored, as the scale is not processed.
Only the shapes on the current scale are displayed, when the current scale is changed shapes will be displayed accordingly.
A green line on top of each box indicates that the scale has shapes associated with it.
Fine detail scales can only be seen at certain zoom level, a light gray line on top of each box will indicate that the scale is visible at current zoom level.
The top slider adjusts the merge scale feature. This setting allows to apply a common edit on multiple consecutive scales within a group starting from the highest scale (not including the residual image) down to the one selected by this slider. If the slider is set to 3 and the maximum scale is 5 then all edits that are added to scale 5 will be applied to scales 3 to 5. Edits added to scale 4 will be applied to scales 3 and 4, and edits added to scale 3 will be applied only to scale 3. Merged scales are represented by a green-yellow color. A value of zero means that the merge feature is not used.
The display wavelet scale button (
) allow to view the current wavelet scale. The module's blend feature is temporary
disabled when this option is set. If blending in the module is active and the option to
display masks is active this option cannot be set. When this option is active a new
section, “preview single scale”, will be displayed, allowing to adjust the
levels for the displayed image. This is purely a convenience feature so you can adjust
wavelet scale display to your needs. It does not have an effect on the final output
image. An auto levels button (
) is also available; it works on the displayed image, so different results can be
expected depending on the image displayed when zoomed in/out. Levels are only applied to
detail scales, not the original or residual image.
The cut and paste buttons allow to move all the shapes from one scale to another. In
order to do this first select the current scale, click the cut button (
), select the destination scale and click paste (
). This can be useful when there are edits on the residual image and one has to change
the number of scales; since the residual image is changed, shapes need to be moved to
the new one.
The switch off shapes button (
) temporarily disables the processing of all shapes for a simple before/after
comparison.
The display masks button (
) works similar to the one on the blend module, but it will display only the shapes on
the current scale. This option and display mask on the blend module cannot be set at the
same time.
The shapes toolbar allows to add new shapes to the image. Shapes creation/editing behaves like in the spot removal module. In addition, by Ctrl+click on any shape button, the continuous add mode is activated. Once a shape is added, darktable will remain in creation mode, allowing to add another shape of the same type. To change the shape type to be added Ctrl+click on a different shape button to continue on continuous add mode or plain click to add a single shape. To leave the continuous add mode right click on any clear area of the image.
The algorithms toolbar allows to select between heal (
), clone (
), fill (
) and blur (
) algorithms. Before actually creating a shape the algorithm must be
selected – once a shape is created the algorithm cannot be changed.
Any combination of shape type and algorithm can be added to the image.
The shape selected field displays the selected shape (if any). To select a shape click on it, to deselect click on a free area on the image.
Mask opacity is displayed when a shape is selected. It displays/sets the opacity of the mask. Opacity is a property of the currently selected shape and won't be used as default value for newly added shapes.
Different properties will be displayed depending on the selected algorithm:
| fill algorithm |
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| blur algorithm |
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The value set on each one of these properties is used as a default when a new shape is created.
This module uses some of the shapes that are offered in drawn masks, namely circles, ellipses and path shapes. The user interface and the controls are the same as in drawn mask and explained in more detail in Section 3.2.5.5, “Drawn mask”.
Select the desired shape by clicking the corresponding icon, then click on the canvas to choose the area to be healed, i.e. the target area. A cross is displayed where the source area will be positioned.
The source positioning has two modes: absolute or relative. To set the absolute mode, while creating a shape, Shift+Ctrl+click on the desired position. From now on, all new shapes will have the source created at that position. To set the relative mode, still while creating a shape, Shift+click on the desired position. The current shape will have the source created at that position and the subsequent ones will have the source created at the same relative position.
After creation source area and target area can be shifted independently until the result matches your expectations. An arrow helps to tell source from target area.
Use the shape specific controls to adjust its size, its border width, and other attributes.
Right-click on a shape to delete it.
Collapse the module to complete the changes.
| The liquify module offers a versatile way of moving pixels around by applying free style distortions to parts of the image. There are three tools to help doing that: points, lines, and curves. |
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Each of liquify's tools is based on nodes. A point is given by a single node, a line or a curve consist of a set of nodes defining the path.
There is a limit of 100 nodes in a single liquify instance. For more distortions one can use multiple instances of the liquify module. However, take into account that the liquify module requires a lot of computing resources.
| The basic elements of all tools in liquify are nodes. |
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You can drag the central point of a node to move the node around. The radius describes the area of the applied effect: the distortion occurs only inside this radius. To change the radius drag the handle at the circumference. A strength vector starting from the center describes the direction of the distortion, and its strength is depicted by the length of the vector. You change the vector by dragging its arrowhead.
This information field displays the number of warps (individual distortion object) and nodes currently used.
Click the
icon to activate the point tool and left-click on the image to place it.
A point is formed by a single node. In a point the strength vector has three different modes which are toggled using Ctrl+click over the arrowhead of the strength vector:
| linear | The linear mode produces a linear distortion inside the circle. Starting from the opposite side of the strength vector and following the strength vector's direction. This is the default mode. |
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| radial growing | In this mode the strength vector's effect is radial, starting with a strength of 0% in the center and growing when going away from the center. This mode is depicted by an additional circle with the arrow pointing outwards. |
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| radial shrinking | In this mode the strength vector's effect is radial, starting with a strength of 100% in the center and shrinking when going away from the center. This mode is depicted by an additional circle with the arrow pointing inwards. |
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Note that the strength by default varies linearly from 0% to 100% between the center and the radius of the control point. It is possible to modify the feathering effect by clicking on the center of the circle:
| default | Linear from the center to the radius. |
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| feathered | Two control circles are displayed and can be modified independently to feather the strength of the effect. Note that clicking again the center of the circle only hides the feathering controls but does not return to the default. |
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A point can be removed by right-clicking on the center.
Click the
icon to activate the line tool and left-click on the image to place the first point,
move and left-click to place another point and start forming the path. To end the line
just right-click anywhere.
| A line is a set of points. The points are linked together, the effect is interpolated by a set of strength vectors. |
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It is possible to add a control point on a line by Ctrl+Click on a segment. You may remove a control point from a line by Ctrl+right click on the node center.
A right-click on a segment will remove the shape completely.
A Ctrl+Alt+click on a segment will change it to a curve segment.
Click the
icon to activate the curve tool and left-click on the image to place the first point,
move and left-click to place another point and start forming the path. To end the line
just right-click anywhere.
| A curve is a set of points. The points are linked together, the effect is interpolated as a bezier curve by a set of strength vectors. |
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It is possible to add a control point on a curve by Ctrl+click on a segment. You may remove a control point from a curve by Ctrl+right click on the node center.
A right-click on a segment will remove the shape completely.
A Ctrl+Alt+click on a segment will change it to a line segment.
It is possible to change the way the points of the curve are linked together by using Ctrl+click on the center. There are four modes which correspond to different ways of handling the steepness of the bezier curve by control handles:
| autosmooth | This is the default mode in which the control handles are not displayed as they are automatically computed to always give a smooth curve. |
| cusp | Control handles can be moved independently. This mode is depicted by a triangle symbol in the node center. |
| smooth | Control handles are always giving a smooth curve. This mode is depicted by a diamond symbol in the node center. |
| symmetrical | Control handles are always moved together. This mode is depicted by a square symbol in the node center. |
